Pneumatic gauges



Aug. 5, 1958 J.ILOXHAM EI'AL 2,845,791

PNEUMATIC GAUGES Filed 001.. 27, 1955 2 Sheets-Sheet 1 J. LOXHAM ETAL2,845,791

PNEUMATIC amass Aug. 5; 1958 2 Sheets-Sheet 2 Filed Oct. 27, 1955 UnitedStates Patent PNEUMATIC GAUGES John Loxham and Frederick Robert Boosey,L etchworth, England, assignors to The Sigma Instrument Company Limited,Letchworth, England, a British company Application October 27, 1955,Serial No. 543,188

Claims priority, application Great Britain December 30, 1954 4 Claims.(Cl. 73--37.5)

This invention relates to pneumatic gauges.

According to the present invention there is provided a pneumatic gaugecomprising a gauging jet for co-operating with the workpiece to begauged, a pressure indicating device, an air supply pipe leading througha constriction to the jet, a conduit between said device and the part ofsaid pipe that is between the constriction and the jet, a valve in theconduit, and means controlling the valve so that when a workpiece islocated in the gauging position the valve is open and when there is noworkpiece in the gauging position the valve is closed, the arrangementbeing such that during gauging of a workpiece the indication given bysaid device is indicative of the dimension being gauged and such thatwhen the workpiece is removed from the gauging position the valve isclosed before the leakage of the air from the jet changes as the resultof removal of the workpiece from the gauging position, whereby saiddevice maintains said indication after the workpiece has been removedfrom the gauging position.

For a better understanding of the invention and to show how the same maybe carried into effect, reference will now be made to the accompanyingdrawings, in which:

Figure l is a diagrammatic layout of a pneumatic gauge,

Figure 2 is a cross-section of a retaining valve employed in the gaugeof Figure 1, and

Figures 3 and 4 are partly cross-sectioned views of alternative forms ofretaining valve.

The pneumatic gauge now to be described is an improvement on the gaugedescribed in our British patent specification No. 724,205, theimprovement consisting in the addition of means for retaining theindication in the manometer tube, after a workpiece that has been gaugedis removed from the gauging position.

In the present apparatus an air supply pipe 1 divides into threebranches 2, 3, 4. The branch 2 leads through a constriction 5 to theupper end of the manometer tube 6, there being a leak-off valve 7 thatis a'djustableto permit controlled leakage of air from the part of thebranch 2. that is between the constriction 5 and the top of the tube 6.A horizontally disposed flexible diaphragm 8 divides a flat box 9 intoupper and lower compartments 10, 11. The lower compartment 11communicates with the tube 6. The lower compartment 11, the lower partof the tube 6 and the conduit 12 connecting the tube 6 to the lowercompartment 11 contain a liquid 13, e. g. water.

The branch 3 leads through a constriction 14 to the inlet 15 of aretaining valve 16. The outlet 17 of the retaining valve communicateswith the upper compartment of said box 9. That part of the branch 3 thatis between the constriction 14 and the inlet to the retaining valve 16communicates with a gauging caliper 18 having a jet or jets 19 forco-operating with the workpiece 20. In the present instance theworkpiece 20 is a cylinder that is supported in the gauging position bya 2 V-block 21. The caliper 18 has two jets 19 which are arranged forco-operating with the workpiece 20 at diametrally opposed locations.

The retaining valve 16 is such that when opened the inlet 15 theretocommunicates with the outlet 17, and when closed the inlet and outlet donot communicate, escape of air from the outlet being prevented. Theretaining valve 16 may be electrically, mechanically, hydraulically orpneumatically operated. In the present instance a pneumatically operatedarrangement will be described. To this end the branch 4 leads through aconstriction 22 to one end of a cylinder 23 (Figure 2) in a mounting 24that carries the retaining valve 16. That part of the branch 4 that isbetween the constriction 22 and the cylinder 23 communicates with amonitoring jet 25. The monitoring jet 25 is elongated along the axis ofthe workpiece 20 so that its length is two or three times greater thanthe diameter of the gauging jets 19. The gauging jets 19 are located ina plane that is perpendicular to the axis of the workpiece and whichapproximately bisects the monitoring jet 25.

The retaining valve 16 is a Well-known Schrader tire valve. This valvehas a cylindrical casing 26 which has a bore 27 that is slightly widenedtowards the end 27A. A hollow frusto-conical seating member 28 having 'aresilient sealing material 29 on the exterior thereof is inserted in thewider end 27A of the bore 27 until it binds against the wall of the bore27 where the bore begins to narrow. The seating member 28 is held inthis position by a collar 30 screwed into the casing 26. A valve memberin the form of a cup 31 is secured centrally on a pin 32, one end 32A ofwhich is passed through the seating member 28 and the collar 30 toproject beyond the wider end of the casing 26. The mouth of the cup 31faces the periphery of the narrower end of the seating member 28, thisperiphery forming the seat of the valve and co-operating with a rubberwasher (not shown) contained in the cup 31. The other end 32B of the pin32 is passed freely through a retaining member 33, which latter is heldon the pin 32 by a head 34 on the latter. A coiled spring 35 around thepin 32 is located between the retaining member 33 and the bottom of thecup 31. A collar 36 is screwed into the narrower end of the easing 26 toencounter the retaining member 33 and thereby to impart a valve closingforce on the cup 31, through the intermediary of the spring 35. Theforce required to open the valve is, of course, determined by the extentto which the collar 36 is screwed into said narrower end of the casing26. This narrower end of the casing forms the outlet to the retainingvalve.

The end 26A of the casing 26 is secured in the mouth of a recess 37formed in said mounting 24. The inlet 15 of the retaining valvecommunicates with the recess 37. The end 32A of the pin 32 abuts againstone end of a push rod 38 that is slidably carried in the mounting 24,the other end of the push rod 38 being in contact with one side of aflexible membrane 39 that is secured against the wall 23A ofthe/cylinder 23; The membrane 39 covers the opening 40 to the bore 41 inthe mounting 24, in'which bore 41 the push rod 38 is located. One end ofa further push rod 42, located in the cylinder 23 and supported by acollar 23C, co-operates with the other side of the membrane 39 at alocation immediately opposite the end of the push rod 38. The other end42A of the push rod 42 which end is enlarged and located in a recess 23Din the collar 23C contacts the central part of a diaphragm 43 theperiphery of which is secured to the curved wall 23B of the cylinder 23.The recess 23D is vented to atmosphere by ports 44 and 44A.

The apparatus described above operates as follows. Before a workpiece isplaced on the V-block 21 air escapes freely from the monitoring jet 25and hence the pressure applied to the end 23E of the cylinder 23 is lowand the spring 35 maintains the valve 16 in the closed condition. When aworkpiece 20 is placed on the V-block 21, the monitoring jet 25 iseventually fully masked by the workpiece 20. Since, however, themonitoring jet 25 extends beyond the gauging jets 19 in both directions,the monitoring jet 25 will not be masked until the workpiece 20 iscorrectly co-operating with the gauging jets 19' for gauging purposes.Leakage of air from the gauging jets 19 takes place in accordance withthe clearance 1 between these jets 19 and the workpiece 20, and hencethe leakage of air from these jets and consequently the pressure appliedto the inlet is an indication of the diameter of the workpiece. Thisgauging aspect of the present apparatus is described in greater detailin the aforementioned patent specification No. 724,285. When themonitoring jet 25 has been masked by the workpiece 29 (i. e. after thecorrect gauging pressure has been applied to the inlet 15) the pressureon the downstream side of the constriction 22 rises, and the diaphragm43 deflects against the action of the coiled spring 35, the movement ofthe diaphragm 43 being transmitted to the end 32A of the pin 32 throughthe intermediary of the two push rods 42, 38, whereby the retainingvalve 16 opens and the inlet 15 communicates with the outlet 17 by wayof the recess 37, the collar 36, the interior of the frustoconicalmember 28, the annular passage between the periphery of the cup 31 andthe bore of the casing 26, the gap between the pin 32 and the member 33,and the collar 36. The gauging pressure is therefore appliedto the uppercompartment 10 and the level of the liquid 13 assumes a positionidicative of the diameter of the workpiece being gauged. When theworkpiece 20 is removed from the gauging position and immediately themonitoring jet commences to be unmasked, the pressure on the downstreamside of the constriction 22 drops and the retaining valve 16 closes sothat escape of air from the upper compartment 10 is prevented. Thistakes place before any change in pressure at the inlet 15 of theretaining valve 16 and hence the liquid is maintained at said level eventhough the workpiece 20 is removed from the V-block 21. The liquid 13will in fact remain at the same level until another workpiece 20 isplaced in the gauging position and masks the monitoring jet 25.

in an alternative method of operating the Schrader valve 16 the push rod42 (Figure 3) is extended through the cylinder 23 and projects from themounting 24, the pro jecting part 42A co-operating with a pivoted lever45 that forms the armature of an electro-magnet 46. The lever 45 ispivoted at the end 45A and the projecting part 42A co-operates withcentral part of the lever 45, there being a spring 47 connected asbetween the end 4513 of the lever 45 and the mounting 24 to maintain thelever 45 in contact with the push rod 42. The electromagnet 46 isarranged to be energised when there is no workpiece 20 in the gaugingposition. Such energisation moves the lever 45 against the action of thespring 47, and the coiled spring in the retaining valve 16 maintainsthis valve in the closed condition. The electromagnet 46 is de-energisedwhen a workpiece 20 is placed in the gauging position and hence thevalve 16 is opened. In a slightly modified form (Figure 4) the lever 45may be pivoted centrally, the projecting part 42A of the push rod 42co-operating with the end 45A of the lever 45 and the end 4513 of thelever being acted upon by the electromagnet 46. In this case theelectro-rnagnet 46 is unenergised when there is no workpiece 20 in thegauging position, the electro-magnet 46 being energised and the valve 16thereby opened when there is a workpiece 20 in the gauging position.

We claim:

1. A pneumatic gauge for checking a dimension of a workpiece, the gaugehaving a gauging station and comprising a pressure indicating deviceincluding a visible indicator for indicating the pressure applied to thedevice, a gauging jet at the gauging station and providing an outflowwhich is varied by the workpiece being checked, an air supply pipeleading to said jet, a consiricticn in said pipe, a normally closedvalve having an inlet and an outlet and including control means at leastin part between and controlling the coupling of said inlet and saidoutlet, at first conduit connecting said inlet with a part of said pipebetween the constriction and the jet, a second conduit connecting saidoutlet to said device, sensing means at the gauging station fordetermining the presence of a workpiece at the gauging station, meansconnecting said sensing means to said control means to open said valvewith a workpiece placed at the gauging station whereby a gaugingpressure is applied to said device and to close the valve with theworkpiece removed from the gauging station whereby the position assumedby said visible indicator during gauging is retained until anotherworkpiece is placed at the gauging station.

2. A gauge according to claim 1, wherein the sensing means includesmeans forming a monitoring jet for cooperation with the workpiece, abranch pipe connected between said monitoring jet and the part of theair supply pipe on the upstream side of said constriction, and a furtherconstriction in said branch pipe, and wherein the connecting meansincludes a pressure-responsive means for operating said member, and aconduit connected between said pressure-responsive means and the part ofsaid branch pipe on the downstream side of said further constriction.

3. A gauge according to claim 2, adapted for gauging the diameter of acylindrical workpiece, wherein the monitoring jet is elongated in thedirection of the axis of the workpiece to be gauged and extends in bothdirections from a plane perpendicular to said axis and passing throughsaid gauging jet.

4. A gauge according to claim 3, wherein there is a further gauging jet,the two gauging jets being connected together in parallel, both jetsbeing located in said plane and being disposed for co-operating with aworkpiece at diametrically opposed locations.

References Cited in the file of this patent

